The subject matter disclosed herein relates in general to a housing for mounting components to an exterior of an aircraft, and in particular to a composite housing for traffic collision avoidance system (TCAS) type devices that minimizes or prevents the occurrence of corrosion due to environmental contaminants.
In areas of congested airspace or low visibility, it is desirable for a pilot of one aircraft to be warned of the presence of a nearby aircraft so the respective aircraft may maneuver the aircraft to avoid collision. One device, known as a traffic collision avoidance system (TCAS) employs a transponder mounted on the aircraft that communicates with transponders on nearby aircraft. In this way, the aircraft control systems automatically communicate and provide the pilots with appropriate and timely information about nearby aircraft.
TCAS devices are typically mounted on the external surface of the aircraft. In a typical configuration, a commercial aircraft will have two TCAS devices, one mounted on the underside of the aircraft and one mounted on the top side in an area adjacent to the cockpit. The TCAS device has three major components, a metal chassis, a polymer radome, and an antenna assembly. Bonding material is applied about the periphery of the chassis to couple the radome to the chassis and seal the antenna assembly from the external environment.
Since the TCAS devices are mounted on the outside of the aircraft, the devices need to operate over a wide environmental temperature range, typically on the order of −67° F. to 158° F. (−55 C to 70 C). This wide range of operating temperatures places a great deal of stress on the components of the TCAS device. In particular, the bonding layer between the chassis and the radome is subjected to stresses due to the disparity between the coefficients of thermal expansion of the chassis and the radome. Repeated thermal cycling of the TCAS device may then result in a breach in the bonding layer allowing condensation to migrate into the interior portion of the TCAS device. The entry of the condensation may then result in corrosion of the chassis and antenna assembly.
While existing TCAS devices are suitable for their intended purposes, there remains a need for improvements. In particular, there remains a need for improvements in reducing or preventing the infiltration of water and other environmental contaminants into the interior of the TCAS device.